I installed the M*CARBO spring kit in my .40 Shield. 1.0.
I have since replaced their striker spring with the original because I wanted to take no chances with primer ignition.
Great improvement for around $25.
The main improvement IMO was watching their You-Tube parts polishing video, that really improved the smoothness of the pull.
I think they could have included a larger piece of fine grit sandpaper, but I had plenty on hand.
I'm very pleased with the results!